Hi Tom,
I had always simply taken a trailer's "tongue weight" to be the difference between the total weight and the weight borne by the axle(s). That's certainly the way RV manufacturers use it. However, your question made me think about it a little more and I'm not so sure if that's the best definition in the context of our discussions. As soon as we mention "borne by the axle(s)", we're talking about the ground's reaction through the axles, which, as we've clearly illustrated in this thread, is changed by a WD system.
I think instead that the unchanging "tongue weight" that we've discussed would have to be described in terms of gravitational mass, but I'm not sure that there's a simple way to characterize the remaining mass that's not centered over the axle(s).
Care to take a stab at it?
Thanks for the brain ponder. :E
Tim,
My latest line of thinking is this: We have all been trying to define the WD system, when it is "tongue weight" that is giving us the trouble. Since page 1, I have had a problem with saying "tongue weight does not get distributed".
We all know what "tongue weight" means when the TT is sitting alone and the tongue is supported by the tongue jack. Now the problem: We drop the tongue on the ball and crank up on the jack and what happens? The manufacturers suggest by their wording that tongue weight is distributed to and borne mostly on the rear axle. This is the root of the confusion.
From Equal-i-zer:
With ordinary ball-type hitches, most of the trailer tongue-weight gets carried on the back axle of the tow vehicle
, often this raises the front end of the vehicle. The Equal-i-zer transfers the trailer's tongue-weight evenly to all the axles of the tow vehicle. This keeps the steering wheels in firm contact with the road surface -- giving you greater control and safety.
This way of thinking about tongue weight is what led to my initial problem with Ron's explanation of the WD system and tongue weight. My line of thinking was that some of the weight from the tongue was transferred through the hitch ball and receiver and was now borne mostly on the rear axle.
Ron said this in another thread:
Tongue Weight: That portion of the TT weight which is carried on the ball coupler as opposed to that carried on the axles.
Tongue weight, as a percentage of total TT weight, is a measure of the relative location of the TT's center of gravity. When WD bars are tensioned, the
tongue weight does not change.
WD hitch users should not be concerned that their TT's stability will be diminished due to the load transfer created by the hitch.
When WD bars are tensioned, the hitch load does change because some of the downward force exerted by the tensioners on the TT's A-frame is transferred to the TT's axles. The hitch load is reduced by the same amount.
Here is the decision we need to make. If we are to use Ron's definition of tongue weight, then as soon as the TT is connected to a TV, thats when we need to STOP talking about tongue weight, period. We should use terms like hitch load and axle load to describe weight changes.
Unfortunately the manufacturers suggest that tongue weight is transferred to the rear axle of the TV upon ordinary hookup. They are saying that tongue weight has already been distributed and that by using a WD system, tongue weight/load gets redistributed.
Ron has proved that a WD system can transfer load from the rear axle of the TV to the front axle and the TTs axles, regardless of and no matter what the tongue weight is, but we are left with a dilemma as to how to define tongue weight AFTER a WD system is engaged.
